Various polymeric coatings and articles are produced in processes involving the use of organic solvents. There is an intense effort by law makers, researchers, and industry to promote high and 100% solids formulations to reduce or eliminate the use of such solvents and the attendent costs and environmental contamination. These processes require a latent catalyst or latent reaction promoter which can be activated in a controlled fashion.
Thermal curing of polyurethane precursors using reaction promotors such as tin salts and tertiary amines is known in the art. Curing of polymerizable mixtures of polyisocyanates with polyols (referred to as polyurethane precursors) using thermally latent catalysts is known in the art (see for example U.S. Pat. Nos. 4,521,545, and 4,582,861).
Photocuring of urethane (meth)acrylates is well known (see T. A. Speckhard, K. K. S. Hwang, S. B. Lin, S. Y. Tsay, M. Koshiba, Y. S. Ding, S. L. Cooper J. Appl. Polymer Science, 1985, 30, 647-666. C. Bluestein Polym.-Plast. Technol. Eng. 1981, 17 83-93). Photocuring of polyurethane precursors using diazonium salts, tertiary amine precursors, and organotin compounds is also known (see U.S. Pat. Nos. 4,544,466, 4,549,945, and EP No. 28,696, Derwent abstract). All of these methods suffer from one or more of the following disadvantages: sensitivity to oxygen, requirement of ultraviolet and/or high intensity light, the need for modified resins, loss or dilution of urethane properties, low activity, poor solubility, and poor potlife.
The prior art discloses processes for the polymerization of epoxy materials. It is further known that a metallocene, such as ferrocene, can be used as a curing accelerator for epoxy materials (U.S. Pat. No. 3,705,129). U.S. Pat. Nos. 3,709,861, 3,714,006, 3,867,354 and 4,237,242 relate to the use of transition metal complexes in the reaction between polyepoxides and polyfunctional curing additives, but they do not teach the polymerization of epoxide group-containing compositions not containing a curing additive. The polymerization of epoxide group-containing materials is also known. Among such processes are those in which the polymerization catalyst is a radiation-sensitive onium salt of a Lewis acid (e.g. diazonium salts as is described in U.S. Pat. Nos. 3,794,576 and 4,080,274; halonium salts as is disclosed in U.S. Pat. No. 4,026,705; and the onium salts of Group VIA elements, particularly the sulfonium salts, as are disclosed in U.S. Pat. No. 4,058,400), or a dicarbonyl chelate compound of a Group IIIA-VA element as is disclosed in U.S. Pat. No. 4,086,091. These compositions are limited to ultraviolet radiation for polymerization. Furthermore, the dicarbonyl chelates are moisture sensitive.
U.S. Pat. No. 4,216,288 teaches the thermal curing of cationally polymerizable compositions using onium salts and reducing agents.
Energy polymerizable compositions comprising ionic salts of organometallic complex cations and cationically sensitive materials and the curing thereof has been taught (see European Patent Document Nos. 109,851; 094,914, Derwent abstract; and 094,915, Derwent abstract).
Neutral organometallic compounds have been used in combination with neutral halogenated compounds for the photocuring of ethylenically-unsaturated monomers. (G. Smets, Pure G. Appl. Chem., 53, 611,615 (1981); H. M. Wagner, M. D. Purbrick, J. Photograph Science, 29, 230-235 (1981).
The use of certain photosensitizers with onium salts for initiation of polymerization of ethylenically-unsaturated monomers is also well known in the art. This technique has found applications in printing, duplication, copying, and other imaging systems (see J. Kosar in Light Sensitive Systems: Chemistry and Application of Nonsilver Halide Photographic Processes, Wiley, New York, 1965, pp 158-193). Aryliodonium salts have been previously described for use as photoinitiators in addition-polymerizable compositions. (See U.S. Pat. Nos. 3,729,313, 3,741,769, 3,808,006, 4,228,232, 4,250,053 and 4,428,807; H. J. Timpe and H. Baumann, Wiss Z. Tech. Hochsch. Leuna-Merseburg, 26, 439 (1984); H. Baumann, B. Strehmel, H. J. Timpe and U. Lammel, J. Prakt. Chem., 326 (3), 415 (1984); and H. Baumann, U. Oertel and H. J. Timpe, Euro. Polym. J., 22 (4), 313 (Apr. 3, 1986).
Radiation dual curable compositions containing ethylenically unsaturated monomers and epoxy monomers have been described in U.S. Pat. Nos. 4,156,035, 4,227,978, and 4,623,676. These compositions include onium salts combined with organic compounds as the curing agent, but do not contain any organometallic compounds.
The dual curing of acrylate/polyurethane precursor mixtures is known but these curing methods are not entirely photoactivated nor are any methods known that provide for the simultaneous curing of the polyurethane precursors and acrylates (see U.S. Pat. No. 4,432,793 and Roesler, Modern Paint and Coatings, Apr., 1986, pages 46-55).
U.S. Pat. No. 4,677,137 teaches the use of one of a supported onium salt or an ionic salt of organometallic complex as an initiator of the polymerization of cationically polymerizable materials. The reference does not teach the combination of an ionic salt of an organometallic complex and an onium salt as photoinitiators.
U.S. Pat. No. 4,740,577 and EPO No. 0 250 364 teach the use of an ionic salt of an organometallic complex combined with polyurethane precursors in an energy polymerizable composition. The references do not disclose the use of an onium salt with the ionic salt of an organometallic complex for curing polyurethane precursors.
U.S. Pat. No. 4,707,432 teaches a free radically polymerizable composition comprising a free radically polymerizable material and a photoinitiator system comprising an alpha-cleavage or homolytic bond cleavage photoinitiator and a ferrocenium salt. The reference does not teach the combination of an onium salt with the ionic salt of an organometallic complex. They teach specifically that the free radical initiator is not an onium compound.
EP Nos. 126712 and 152377 (Derwent Abstracts) disclose hardenable composition contain a radical and/or cationically polymerizable material, or their mixtures and at least one ferrous-aromatic complex compound and at least one electron-acceptor as oxidising agent. Onium salts are not disclosed.
GB No. 2191199A, published Dec. 9, 1987, teaches the combination of an onium salt with the ionic salt of an organometallic complex for polymerization of compositions by irradiating at two different wavelengths. The reference does not teach the simultaneous initiation of the polymerization of two different polymerizable materials nor do they demonstrate the enhanced thermal stability derived from this composition. The reference does not teach the polymerization of polyurethane precursors, nor does it teach that such compositions cure faster and have increased stability.